Method for the production of a granulated soap product



Aug. 9, 1955 F. G. PACKARD 2,715,110

METHOD FOR THE PRODUCTION OF A GRANULATED SOAP PRODUCT 2 Sheets-Sheet 1Filed June 13, 1952 FREEMAN G. PACKARD ry/s ATTOENEVS Aug. 9, 1955 FiledJune 13, 1952 SOAP FROM SPRAY DRIER.

F. e. PACKARD 2,715,110

METHOD FOR THE PRODUCTION OF A GRANULATED SOAP PRODUCT 2 Sheets-Sheet 2FiGB.

POWDER COOLER TO PACKING MA IN VEN TOR. FREEMAN G. PACKARD IWETHQD FQRTHE PRODUCTION OF A GRANULATED SGAP PRODUCT Application June 13, 1952,Serial No. 293,235

Claims. (Cl. 2s2 1o9 This invention relates to a method for theproduction of a non-agglomerating granulated soap product.

Granulated soap products, such as spray-dried soap particles especiallywhen freshly packed, exhibit a tendency to gel or agglomerate whenpoured into hot water. The aggregates of sticky soap thus formed areditficult to disperse and dissolve.

The tendency of spray-dried soaps to agglomerate has been demonstratedin the laboratory by pouring the soap on the surface of water, at 120F., in a dishpan, agitating the water gently by hand for a short timeand observing the agglomerates floating on the water. This method,although representing the condition that might prevail in actual usage,does not lend itself to the measurement of comparative degrees ofagglomeration, and it is thus difficult to evaluate the characteristicsof different soaps by such a test unless they are tested simultaneously.A modified test incorporating mechanical agitation and a controlledmethod of adding the soap power was, therefore, developed. In this test,the time required to disperse the soap agglomerates was taken as ameasurement of the degree of agglomeration.

In this test, a dishpan was filled with nine quarts of water,

heated to 120 F. An agitating paddle rotating at 45 R. P. M. wasimmersed in the water so that there was no vortex on the surface of thewater. Thirty-five grams of the soap was poured through a funnel onto adeflecting plate and was thus spread over the surface of the water. Theagitating paddle was run for seconds after pouring the soap in thefunnel, and it was then shut off. The appearance of the soap was thenclassified as heavy gel, moderate gel or loose fioc. After waiting forseconds, the agitating paddle was started again and the time required todisperse or dissolve the gel or floc was noted.

Since agglomeration is apparently caused by particles of soap melting orfusing together, the possibility of preventing agglomeration byintimately mixing a finely pulverized inorganic salt with a spray-driedsoap was considered as a possible solution to the problem. The followingmaterials were used for this purpose at a level of 5% of the totalweight of soap powder, but no measurable improvement in agglomeratingcharacteristics was obtained:

NaCl NazSOr N34P207 Na3PO4 NazCOs NaHCOa Solutions of these materialswere also sprayed onto the soap particles and the product subsequentlywas ovendried to remove excess moisture. Little, if any, improvement inagglomerating properties resulted from this treatment, however.

It has now been found, in accordance with this invention, that theagglomerating tendencies of silicate-containing graular soap productscan be eliminated by treating the substantially dry granules of soapwith carbon dioxide gas. The treatment with carbon dioxide gas resultsin ice the precipitation of free silica particles on the surface of thegranules, which it is found minimizes the agglomerating tendencies ofthe soap.

The presence of inorganic builders such as phosphates in the soapformulation is significant in obtaining a nonagglomerating product bycarbonation, although the formation of free silica is not markedlyaffected when these materials are eliminated from the formula.Experimental soap formulations having varying amounts and proportions ofinorganic builders including silicates, sodium carbonate and tetrasodiumpyrophosphate all show a tendency to agglomerate when the freshlyprepared powders are added to hot water at temperatures of from to F.After the same powders have been exposed to an atmosphere consistingessentially of carbon dioxide for approximately 10 seconds,agglomeration is, from a practical standpoint, eliminated.

Suflicient carbonation to effect the surface formation of free silica isnecessary to insure practical non-agglomerating properties in currentsoaps. This requires the absorption of carbon dioxide by the finishedpowder. It has been found that amounts of free silica formed inaccordance with the invention have no significant effect upon the useproperties of the product.

it has been established that if there is no silicate present in the soapformulation, treatment with CO2 gas does not improve the agglomeratingcharacteristics of the soap. The amount of silicate which may be presentin the soap varies from about 5.0% by weight to about 20.0% by weight.Any of the well-known silicates commonly used in soap formulations maybe employed, for example, the sodium silicates.

it is also desirable to incorporate a phosphate in the soap formulation.The incorporation of the phosphate results in the desirable feature thatthe dispersing time of the soap agglomerates, if any, is greatlyreduced.

Well-known phosphates commonly employed in soap formulations may beused, such as trisodium phosphate, tripolyphosphate and tetrasodiumpyrophosphate.

The invention will be further illustrated by reference to theaccompanying drawings, in which,

Figure l is a front view in elevation and in section, taken on line 11of Figure 2, of a cascade tower for treating soap granules with CO2;

Figure 2 is a side view in elevation of the cascade tower shown inFigure 1; and

Figure 3 shows another apparatus which may be used to treat soapgranules with CO2 in which the soap granules are passed through anatmosphere of CO2 gas between the spray drier and the cooling tower.

Referring specifically to Figure 1, the tower 2 is provided with a feedhopper 4 for the soap granules, having a vibrator 6 attached theretowhich assists the flow of the granules through the feed hopper. Thetower contains a plurality of shelves or baffles 8, which may be at anangle, and which serve to provide a cascading effect to the soapgranules passing downwardly through the tower.

Carbon dioxide gas is introduced through the line 10, preferably at apoint below the first shelf, as shown in Figure 2, in order to reducethe leakage of CO2 from the top of the tower. Since the CO2 gas isheavier than air, it will pass downwardly through the tower. Gas lossesfrom the bottom of the tower are minimized by counterweighted hingeclosure 12.

The rate of CO2 gas flow into the tower may be measured by a calibratedrotameter in the line 10 (not shown). The gas concentration at severallocations in the tower may be determined by withdrawing samples throughthe lines 14, 16 and 18 into a C02 concentration measuring apparatus 29,as shown in Figure 2. The measuring apparatus 24) compares the thermalconductivity of the sample with that of air by means of a calibratedbalanced bridge, as is well known in the art.

Figure 3 shows an alternative arrangement for treating the soap granuleswith CO2 gas in which a hopper 22 is mounted below the conventionalspray drier and receives the dried soap granules. The granules passthrough a flexible rubber connection 24 into an encloseddirectional-throw vibrating conveyor 26 which is supported by thesprings 28 from the ceiling of the building.

A plurality of sampling ports 30 are provided on the top of the conveyorin order that the CO2 gas concentration at various locations in theconveyor housing may be measured. A flexible hose 32 is connected to theright-hand end of the conveyor as viewed in Figure 3 and at its oppositeend to a rotameter 34 which is used to control the volume of CO2 gaspassing into the vibrating conveyor. A CO2 input line 36 is connected tothe rotameter and to any convenient source of CO2 gas and is providedwith a pressure reducer 38, a pressure gauge 40 and a valve 42.

When the granules reach the left-hand end of the vibrating conveyor asviewed in Figure 3, they pass through a flexible connection 44 into aduct 46 connected to a powder cooler 48. From the powder cooler 48, thecooled granules are conveyed to packing machines, not shown.

The invention will be further illustrated by reference to the followingspecific examples:

EXAMPLE 1 A soap powder having the following formula:

Percent Fatty acids 55.00 Anhydrous soap 59.54 Tetrasodium pyrophosphate7.00 Sodium carbonate 2.50

Sodium silicate 12.00

Sodium chloride 4.42185 Glycerin 0.31 Perfume 0.04

Moisture 14.00

Miscellaneous 0.02815 was introduced into the tower shown in Figures 1and 2 at a rate of 2,550 pounds per hour. CO2 gas was then introducedinto the tower at the rate of 37 pounds per hour, which corresponds to1.45% CO2 calculated on the powder weight. The CO2 concentration in thetower was 58% at the top, 27% in the middle, and 13% at the bottom. Itwas found that by treating the powder for from 7 to 9 seconds underthese conditions, a substantially non-agglomerating powder was produced.The powder entered the tower at a temperature of 87 F. and flowed fromthe bottom thereof at 100 F. indicating an appreciable heat of reaction.

EXAMPLE 2 A powder having the same formula as that used in Example 1 wasintroduced into the tower shown in Figures 1 and 2 at a rate of 4,100pounds per hour. CO2 gas was introduced into the tower at the rate of28.8 pounds per hour, corresponding to 0.7% CO2 calculated on the powderweight. The CO2 concentration in the atmosphere in the tower was 44% atthe top, 16% in the middle and 2.5% at the bottom.

Operating under these conditions, a powder having much less tendency toagglomerate was produced.

EXAMPLE 3 A powder having the same formula as that used in Example 1 wasintroduced into the tower shown in Figures 1 and 2 at the rate of 1,275pounds per hour. CO2 gas was introduced into the tower at the rate of13.7 pounds per hour, corresponding to 1.08% CO2 calculated on thepowder weight. The CO2 concentration in the atmosphere of the tower was42% at the top, 27% in the middle and 13% at the bottom.

Comparison of these results with those obtained in Example 2 aboveindicates that better stripping efliciency is obtained when the toweroperates close to maximum capacity.

EXAMPLE 4 To ascertain the etfect obtained when the tower was doubled inheight, a powder having the same formula as that of Example 1 was passedthrough the tower shown in Figures 1 and 2 twice. The powder wasintroduced into the tower at the rate of 1,275 pounds per hour on thefirst pass and 1,280 pounds per hour on the second pass. CO2 gas wasintroduced into the tower at the rate of 13.7 pounds per hour on thefirst pass and 2.0 pounds per hour on the second pass corresponding to1.08% CO2 on the powder weight of the first pass. The gas was added onthe second pass to simulate conditions halfway down a 20 foot tower. TheCO; concentration in the atmosphere in the tower was 42% at the top onthe first pass and 11% on the second pass, 27% at the middle on thefirst pass and 5% on the second pass, and 13% at the bottom on the firstpass and 1% on the second pass.

The powder was substantially non-agglomerating even though only 1.08%CO2 was used. That improved stripping may be anticipated in a highertower is shown by the lower CO2 content of the air at the bottom of thetower on the second pass.

EXAMPLE 5 A series of formulations was prepared wherein sodium carbonateand tetrasodium pyrophosphate were eliminated from the product. Theproducts were carbonated using 3% CO2 and were subsequently tested foragglomeration and the presence of free SiOz. The results indicate thatthe elimination of sodium carbonate and tetrasodium pyrophosphate doesnot markedly affect the formation of silica, but reduces the improvementin agglomerating characteristics that results from carbonation. Theelimination of sodium carbonate alone has no adverse effect. Testresults using various soap formulae are as follows:

A nalylical (percent) NazCOa NaHCO: Na4P2O1 Standard Soap (percent):

Soap,

NaCl, 3.86 .I Tetrasodium pyrophosphate,

T'Jntreated 3% CO2 treated Soap without N21100::

Tetra sodium pyrophosphate,

NazC03, None 3% CO2 treated Soap without NazCOs or tetrasodiumpyrophosphate:

Soap, 68.20

3% C 02 treated Agglomerating tests EXAMPLE 6 A series of samples wasprepared by exposing weighed amounts of fresh soap, having a formula thesame as that employed in Example 1, to varying amounts of carbon dioxidein order to determine the minimum amount of carbonation required toobtain a non-agglomerating product. Carbon dioxide in the form of DryIce line than that of the powder remaining on the screen as shown by thefollowing figures:

pH of 02% solution Untreated powder 10.30 Surface powder removed 9.91Residue, after partial removal of surface powder 10.05

Precipitation of free silica in the soap in the crutcher prior to soapdrying was found to be less efiective than exposing the finished powderto CO2 since it results in the formation of a coarse silica that israpidly deposited in the dishpan as the soap is dissolved.

EXAMPLE 7 To evaluate the effect of phosphates in the soap formulationsof the invention, a series of six formulations were prepared using asoap having the same formula as that of Example 1 except that 7% ofvarious phosphates were added to the formulations.

After similar treatment with CO2 gas, the various soap formulations wereanalyzed and the dispersing time of the soap granules in accordance withthe standard test hereinbefore set forth was measured. The results areas follows:

Formula Percent 0 02 level Free Percent Percent Dispersing sioz NazC O3NaHCOa Time, sec.

gaunugmev- Tetrasodium pyrophosphate Tetrasodium pyrophosphate Trisodiumphosphate Trisodium phosphate. Tripolyphosphate..--..

Tripolyphosphate None (control) Nil 2. 82 Nil 35 (gel). 2.3%- 3. 7 3. 832 98 0 (floc).

Nil 3. 57 N11 40 (gel) 2.0% 1. 58 6. 48 l. 18 10 (i100). None (control)Nil 3. 40 Nil 25 (gel). 2.0% 3. 24 4. 12 3. 17 7 (tloo).

was added to the soap in the flask and was shaken until the carbondioxide was completely vaporized. The agglomerating characteristics ofthe several samples were then determined by the dishpan test. Thisseries of tests indicated that it was necessary for carbonation to takeplace to the extent that the product contained approximately 1.5% freesilica. Large amounts of silica gave a non-agglomerating product, butexcessive quantities might prove to be objectionable in other use tests.The chemical changes occurring in the standard soap formulation ofExample 1 at diiferent stages of carbonation are shown in the followingtable:

It is apparently necessary to neutralize some of the excess sodium oxidein the silicate before any significant amount of SiOz is precipitatedindicatng that higher ratio silicates would be desirable. Batchesprepared using (1) NazO:(2.71)SiO2, and (2) Na2O:(3.25)SiO2substantiated this, non-agglomerating products being obtained withlesser amounts of CO2 when the 3.25 ratio silicate was used.

The precipitation of free silica by carbon dioxide is probably a surfacereaction. This was demonstrated by carbonating a standard soap productand then removing part of the outer surfaces of the particles by gentlyrubbing the particles on a fine mesh screen. The pH of the 0.2%solutions of the surface powder was less alka- From the above results,it is seen that when trisodium phosphate was used in place oftetrasodium pyrophosphate, the free silica formation during treatmentwith CO2 gas was retarded to a considerable extent, although the productwas non-agglomerating. These data indicate that the alkalinity of theproduct during gaseous treatment has some relation to the reaction, andit is believed that the stability of the sodium silicate present in asoap formulation is related to the alkali content in the product inwhich it is used. It is to be expected that a very alkaline phosphatewould have a greater afijnity for CO2 and thus the formation of freesilica would be retarded.

The liberation of free SiOz by C02 gas treatment is effective withgreater ease by increasing the Na2O.SiOz ratio in soap to higher valuesof SiOz relative to the NazO and it has been found that the free silicadevelopment is proportional to the formation of NaHCOs. Using the soapformulation of Example 1, it was found that the free silica developmentbegan when the Na2O.2SiO2 ratio of the sodium silicate present in thatsoap formulation reached approximately 3.16.

EXAMPLE 8 Two experimental soap formulae were prepared. The finishedformulae were as follows:

CO2 gas treatment of these products was completed in the apparatus shownin Figure 3 on a full production scale. Production rates ranged in thevicinity of 10,000 pounds per hour and CO2 was introduced into theconveyor at rates varying from 140 pounds per hour to 250 pounds perhour. The product obtained at the lowest CO2 feed rate was notsatisfactory.

Operating at the rate of 200 lbs. of CO2 per hour with the soap offormula B being conveyed at the rate of 10,000 lbs. per hour produced aproduct having approximately 2.25% SiOz on the surface of the soapparticles. Operating at the higher rate of 240 lbs. of CO2 per hour withthe soap of formula A produced a product having 1.22% SiOz on thesurface thereof.

Results of several production runs are as follows:

It has been indicated heretofore that the extent of the carbon dioxidetreatment should be such as to give a product having satisfactorynon-agglomerating properties. This will depend to a large extent uponthe amount of the silica on the surface of the product and also upon thedepth of the silica formation. In general, products having less thanabout 1% silica deposited primarily on the surface thereof do not showsatisfactory non-agglomerating properties from a commercial acceptancepoint of view.

The length of treatment, the concentration of carbon dioxide in thetreating atmosphere and the amount of carbon dioxide in relation to thesoap product being treated are inter-related and are not critical aslong as the requisite amount of silica is obtained. High carbon dioxideconcentrations permit treating times as short as 3 seconds, and there isno critical upper limit to the treating time. The concentration ofcarbon dioxide, when adjusted to the treating time, may vary from 40% to100% in the treating atmosphere.

In the above disclosure certain soap formulations have been described,but it will be understood that the process can be applied to anysilicate containing soap. In the above example the soap consistedessentially of the sodium salt of fatty acids of tallow, but thepotassium salt may be employed, and the fatty acids may be derived fromother animal and vegetable fats as is well known in the soap industry.

In addition to containing a silicate within the range mentionedheretofore, the soap may be built with any of the common builders suchas the phosphates mentioned heretofore, carbonates and in generalalkaline salts, and other ingredients. The proportions of soap tosilicate and the proportions of soap to builders is not critical and theinvention is applicable to any of the formulations in which soap is theprimary ingredient and contains a silicate.

The silicate is usually the sodium silicate but any other alkali metalmay be used, having the formula, using sodium as illustrative,(Na2O)I.(SiOz) where x and y may be in the range of about 1:1 to 1:3.25or higher.

It is also well known that freshly spray-dried soap, although dry inappearance, contains about 5 to 20% moisture and such soap products canbe treated in the process.

It will be obvious that many soap formulations may be treated inaccordance with the invention and a wide variety of equipment andprocessing techniques will be obvious to those skilled in the art. Theseare intended to be included within the scope of the invention when theyor their equivalents are embraced within the following claims.

I claim:

1. The method for making a granular soap product rapidly dispersible inwater and substantially free from gel forming and agglomeratingcharacteristics comprising preparing an alkali-metal silicate-containingsoap and treating said soap material when in granular form with carbondioxide in a concentration and for a time sufficient to form silica onthe surfaces of said granulated soap particles but insufficient to makethe particles substantially water-insoluble.

2. The method for making a granular soap product rapidly dispersible inwater and substantially free from gel forming and agglomeratingcharacteristics comprising preparing an alkali-metal silicate-containingsoap, spray drying said soap material and treating said soap materialwhen in a spray-dried granular form with carbon dioxide for a timesuflicient to form silica on the surfaces of said granulated soapparticles but insufficient to make the particles substantiallywater-insoluble.

3. The method for making a granular soap product rapidly dispersible inwater and substantially free from gel forming and agglomeratingcharacteristics comprising preparing an alkali-metal silicate-containingsoap, treating said soap material when in granular form with carbondioxide for a time sufiicient to form silica on the surfaces of saidgranulated soap particles but insufiicient to make the particlessubstantially water-insoluble and packaging said treated granular soapproduct.

4. The method for making a granular soap product rapidly dispersible inwater and substantially free from gel forming and agglomeratingcharacteristics comprising preparing a soap containing an alkali-metalsilicate and treating said soap material when in granular form withcarbon dioxide for a time sulficient to form at least about one per centof silica primarily on the surface of said soap particles butinsufficient to make the particles substantially water-insoluble.

5. A method for making a substantially dry, granular, alkali-metalsilicate-containing soap product rapidly dispersible in hot as well ascold water and substantially free from gel-forming and agglomeratingcharacteristics which comprises treating the substantially dry soapgranules with carbon dioxide in a concentration and for a timesuflicient to form silica on the surfaces of the granulated soapparticles but insufficient to make the particles substantiallywaterinsoluble.

References Cited in the file of this patent UNITED STATES PATENTS1,779,517 Stevenson et al. Oct. 28, 1930 1,843,576 McClore et a1. Feb.2, 1932 1,968,628 Alton July 31, 1934 2,386,337 Moyer Oct. 9, 1945

5. A METHOD FOR MAKING A SUBSTANTIALLY DRY, GRANULAR, ALKALI-METALSILICATE-CONTAINING SOAP PRODUCT RAPIDLY DISPERSIBLE IN HOT AS WELL ASCOLD WATER AND SUBSTANTIALLY FREE FROM GEL-FORMING AND AGGLOMERATINGCHARACTERISTICS WHICH COMPRISES TREATING THE SUBSTANTIALLY DRY SOAPGRANULES WITH CARBON DIOXIDE IN A CONCENTRATION AND FOR A TIMESUFFICIENT TO FORM SILICA ON THE SURFACES OF THE GRANULATED SOAPPARTICLES BUT INSUFFICIENT TO MAKE THE PARTICLES SUBSTANTIALLYWATER-INSOLUBLE.